Unix/Linux Go Back    


CentOS 7.0 - man page for pod::parser (centos section 3)

Linux & Unix Commands - Search Man Pages
Man Page or Keyword Search:   man
Select Man Page Set:       apropos Keyword Search (sections above)


Pod::Parser(3)		       User Contributed Perl Documentation		   Pod::Parser(3)

NAME
       Pod::Parser - base class for creating POD filters and translators

SYNOPSIS
	   use Pod::Parser;

	   package MyParser;
	   @ISA = qw(Pod::Parser);

	   sub command {
	       my ($parser, $command, $paragraph, $line_num) = @_;
	       ## Interpret the command and its text; sample actions might be:
	       if ($command eq 'head1') { ... }
	       elsif ($command eq 'head2') { ... }
	       ## ... other commands and their actions
	       my $out_fh = $parser->output_handle();
	       my $expansion = $parser->interpolate($paragraph, $line_num);
	       print $out_fh $expansion;
	   }

	   sub verbatim {
	       my ($parser, $paragraph, $line_num) = @_;
	       ## Format verbatim paragraph; sample actions might be:
	       my $out_fh = $parser->output_handle();
	       print $out_fh $paragraph;
	   }

	   sub textblock {
	       my ($parser, $paragraph, $line_num) = @_;
	       ## Translate/Format this block of text; sample actions might be:
	       my $out_fh = $parser->output_handle();
	       my $expansion = $parser->interpolate($paragraph, $line_num);
	       print $out_fh $expansion;
	   }

	   sub interior_sequence {
	       my ($parser, $seq_command, $seq_argument) = @_;
	       ## Expand an interior sequence; sample actions might be:
	       return "*$seq_argument*"     if ($seq_command eq 'B');
	       return "`$seq_argument'"     if ($seq_command eq 'C');
	       return "_${seq_argument}_'"  if ($seq_command eq 'I');
	       ## ... other sequence commands and their resulting text
	   }

	   package main;

	   ## Create a parser object and have it parse file whose name was
	   ## given on the command-line (use STDIN if no files were given).
	   $parser = new MyParser();
	   $parser->parse_from_filehandle(\*STDIN)  if (@ARGV == 0);
	   for (@ARGV) { $parser->parse_from_file($_); }

REQUIRES
       perl5.005, Pod::InputObjects, Exporter, Symbol, Carp

EXPORTS
       Nothing.

DESCRIPTION
       Pod::Parser is a base class for creating POD filters and translators.  It handles most of
       the effort involved with parsing the POD sections from an input stream, leaving subclasses
       free to be concerned only with performing the actual translation of text.

       Pod::Parser parses PODs, and makes method calls to handle the various components of the
       POD. Subclasses of Pod::Parser override these methods to translate the POD into whatever
       output format they desire.

       Note: This module is considered as legacy; modern Perl releases (5.18 and higher) are
       going to remove Pod::Parser from core and use Pod::Simple for all things POD.

QUICK OVERVIEW
       To create a POD filter for translating POD documentation into some other format, you
       create a subclass of Pod::Parser which typically overrides just the base class
       implementation for the following methods:

       o command()

       o verbatim()

       o textblock()

       o interior_sequence()

       You may also want to override the begin_input() and end_input() methods for your subclass
       (to perform any needed per-file and/or per-document initialization or cleanup).

       If you need to perform any preprocessing of input before it is parsed you may want to
       override one or more of preprocess_line() and/or preprocess_paragraph().

       Sometimes it may be necessary to make more than one pass over the input files. If this is
       the case you have several options. You can make the first pass using Pod::Parser and
       override your methods to store the intermediate results in memory somewhere for the
       end_pod() method to process. You could use Pod::Parser for several passes with an
       appropriate state variable to control the operation for each pass. If your input source
       can't be reset to start at the beginning, you can store it in some other structure as a
       string or an array and have that structure implement a getline() method (which is all that
       parse_from_filehandle() uses to read input).

       Feel free to add any member data fields you need to keep track of things like current
       font, indentation, horizontal or vertical position, or whatever else you like. Be sure to
       read "PRIVATE METHODS AND DATA" to avoid name collisions.

       For the most part, the Pod::Parser base class should be able to do most of the input
       parsing for you and leave you free to worry about how to interpret the commands and
       translate the result.

       Note that all we have described here in this quick overview is the simplest most
       straightforward use of Pod::Parser to do stream-based parsing. It is also possible to use
       the Pod::Parser::parse_text function to do more sophisticated tree-based parsing. See
       "TREE-BASED PARSING".

PARSING OPTIONS
       A parse-option is simply a named option of Pod::Parser with a value that corresponds to a
       certain specified behavior. These various behaviors of Pod::Parser may be enabled/disabled
       by setting or unsetting one or more parse-options using the parseopts() method.	The set
       of currently accepted parse-options is as follows:

       -want_nonPODs (default: unset)
	  Normally (by default) Pod::Parser will only provide access to the POD sections of the
	  input. Input paragraphs that are not part of the POD-format documentation are not made
	  available to the caller (not even using preprocess_paragraph()). Setting this option to
	  a non-empty, non-zero value will allow preprocess_paragraph() to see non-POD sections
	  of the input as well as POD sections. The cutting() method can be used to determine if
	  the corresponding paragraph is a POD paragraph, or some other input paragraph.

       -process_cut_cmd (default: unset)
	  Normally (by default) Pod::Parser handles the "=cut" POD directive by itself and does
	  not pass it on to the caller for processing. Setting this option to a non-empty, non-
	  zero value will cause Pod::Parser to pass the "=cut" directive to the caller just like
	  any other POD command (and hence it may be processed by the command() method).

	  Pod::Parser will still interpret the "=cut" directive to mean that "cutting mode" has
	  been (re)entered, but the caller will get a chance to capture the actual "=cut"
	  paragraph itself for whatever purpose it desires.

       -warnings (default: unset)
	  Normally (by default) Pod::Parser recognizes a bare minimum of pod syntax errors and
	  warnings and issues diagnostic messages for errors, but not for warnings. (Use
	  Pod::Checker to do more thorough checking of POD syntax.) Setting this option to a non-
	  empty, non-zero value will cause Pod::Parser to issue diagnostics for the few warnings
	  it recognizes as well as the errors.

       Please see "parseopts()" for a complete description of the interface for the setting and
       unsetting of parse-options.

RECOMMENDED SUBROUTINE/METHOD OVERRIDES
       Pod::Parser provides several methods which most subclasses will probably want to override.
       These methods are as follows:

command()
		   $parser->command($cmd,$text,$line_num,$pod_para);

       This method should be overridden by subclasses to take the appropriate action when a POD
       command paragraph (denoted by a line beginning with "=") is encountered. When such a POD
       directive is seen in the input, this method is called and is passed:

       $cmd
	  the name of the command for this POD paragraph

       $text
	  the paragraph text for the given POD paragraph command.

       $line_num
	  the line-number of the beginning of the paragraph

       $pod_para
	  a reference to a "Pod::Paragraph" object which contains further information about the
	  paragraph command (see Pod::InputObjects for details).

       Note that this method is called for "=pod" paragraphs.

       The base class implementation of this method simply treats the raw POD command as normal
       block of paragraph text (invoking the textblock() method with the command paragraph).

verbatim()
		   $parser->verbatim($text,$line_num,$pod_para);

       This method may be overridden by subclasses to take the appropriate action when a block of
       verbatim text is encountered. It is passed the following parameters:

       $text
	  the block of text for the verbatim paragraph

       $line_num
	  the line-number of the beginning of the paragraph

       $pod_para
	  a reference to a "Pod::Paragraph" object which contains further information about the
	  paragraph (see Pod::InputObjects for details).

       The base class implementation of this method simply prints the textblock (unmodified) to
       the output filehandle.

textblock()
		   $parser->textblock($text,$line_num,$pod_para);

       This method may be overridden by subclasses to take the appropriate action when a normal
       block of POD text is encountered (although the base class method will usually do what you
       want). It is passed the following parameters:

       $text
	  the block of text for the a POD paragraph

       $line_num
	  the line-number of the beginning of the paragraph

       $pod_para
	  a reference to a "Pod::Paragraph" object which contains further information about the
	  paragraph (see Pod::InputObjects for details).

       In order to process interior sequences, subclasses implementations of this method will
       probably want to invoke either interpolate() or parse_text(), passing it the text block
       $text, and the corresponding line number in $line_num, and then perform any desired
       processing upon the returned result.

       The base class implementation of this method simply prints the text block as it occurred
       in the input stream).

interior_sequence()
		   $parser->interior_sequence($seq_cmd,$seq_arg,$pod_seq);

       This method should be overridden by subclasses to take the appropriate action when an
       interior sequence is encountered. An interior sequence is an embedded command within a
       block of text which appears as a command name (usually a single uppercase character)
       followed immediately by a string of text which is enclosed in angle brackets. This method
       is passed the sequence command $seq_cmd and the corresponding text $seq_arg. It is invoked
       by the interpolate() method for each interior sequence that occurs in the string that it
       is passed. It should return the desired text string to be used in place of the interior
       sequence.  The $pod_seq argument is a reference to a "Pod::InteriorSequence" object which
       contains further information about the interior sequence.  Please see Pod::InputObjects
       for details if you need to access this additional information.

       Subclass implementations of this method may wish to invoke the nested() method of $pod_seq
       to see if it is nested inside some other interior-sequence (and if so, which kind).

       The base class implementation of the interior_sequence() method simply returns the raw
       text of the interior sequence (as it occurred in the input) to the caller.

OPTIONAL SUBROUTINE/METHOD OVERRIDES
       Pod::Parser provides several methods which subclasses may want to override to perform any
       special pre/post-processing. These methods do not have to be overridden, but it may be
       useful for subclasses to take advantage of them.

new()
		   my $parser = Pod::Parser->new();

       This is the constructor for Pod::Parser and its subclasses. You do not need to override
       this method! It is capable of constructing subclass objects as well as base class objects,
       provided you use any of the following constructor invocation styles:

	   my $parser1 = MyParser->new();
	   my $parser2 = new MyParser();
	   my $parser3 = $parser2->new();

       where "MyParser" is some subclass of Pod::Parser.

       Using the syntax "MyParser::new()" to invoke the constructor is not recommended, but if
       you insist on being able to do this, then the subclass will need to override the new()
       constructor method. If you do override the constructor, you must be sure to invoke the
       initialize() method of the newly blessed object.

       Using any of the above invocations, the first argument to the constructor is always the
       corresponding package name (or object reference). No other arguments are required, but if
       desired, an associative array (or hash-table) my be passed to the new() constructor, as
       in:

	   my $parser1 = MyParser->new( MYDATA => $value1, MOREDATA => $value2 );
	   my $parser2 = new MyParser( -myflag => 1 );

       All arguments passed to the new() constructor will be treated as key/value pairs in a
       hash-table. The newly constructed object will be initialized by copying the contents of
       the given hash-table (which may have been empty). The new() constructor for this class and
       all of its subclasses returns a blessed reference to the initialized object (hash-table).

initialize()
		   $parser->initialize();

       This method performs any necessary object initialization. It takes no arguments (other
       than the object instance of course, which is typically copied to a local variable named
       $self). If subclasses override this method then they must be sure to invoke
       "$self->SUPER::initialize()".

begin_pod()
		   $parser->begin_pod();

       This method is invoked at the beginning of processing for each POD document that is
       encountered in the input. Subclasses should override this method to perform any per-
       document initialization.

begin_input()
		   $parser->begin_input();

       This method is invoked by parse_from_filehandle() immediately before processing input from
       a filehandle. The base class implementation does nothing, however, subclasses may override
       it to perform any per-file initializations.

       Note that if multiple files are parsed for a single POD document (perhaps the result of
       some future "=include" directive) this method is invoked for every file that is parsed. If
       you wish to perform certain initializations once per document, then you should use
       begin_pod().

end_input()
		   $parser->end_input();

       This method is invoked by parse_from_filehandle() immediately after processing input from
       a filehandle. The base class implementation does nothing, however, subclasses may override
       it to perform any per-file cleanup actions.

       Please note that if multiple files are parsed for a single POD document (perhaps the
       result of some kind of "=include" directive) this method is invoked for every file that is
       parsed. If you wish to perform certain cleanup actions once per document, then you should
       use end_pod().

end_pod()
		   $parser->end_pod();

       This method is invoked at the end of processing for each POD document that is encountered
       in the input. Subclasses should override this method to perform any per-document
       finalization.

preprocess_line()
		 $textline = $parser->preprocess_line($text, $line_num);

       This method should be overridden by subclasses that wish to perform any kind of
       preprocessing for each line of input (before it has been determined whether or not it is
       part of a POD paragraph). The parameter $text is the input line; and the parameter
       $line_num is the line number of the corresponding text line.

       The value returned should correspond to the new text to use in its place.  If the empty
       string or an undefined value is returned then no further processing will be performed for
       this line.

       Please note that the preprocess_line() method is invoked before the preprocess_paragraph()
       method. After all (possibly preprocessed) lines in a paragraph have been assembled
       together and it has been determined that the paragraph is part of the POD documentation
       from one of the selected sections, then preprocess_paragraph() is invoked.

       The base class implementation of this method returns the given text.

preprocess_paragraph()
		   $textblock = $parser->preprocess_paragraph($text, $line_num);

       This method should be overridden by subclasses that wish to perform any kind of
       preprocessing for each block (paragraph) of POD documentation that appears in the input
       stream. The parameter $text is the POD paragraph from the input file; and the parameter
       $line_num is the line number for the beginning of the corresponding paragraph.

       The value returned should correspond to the new text to use in its place If the empty
       string is returned or an undefined value is returned, then the given $text is ignored (not
       processed).

       This method is invoked after gathering up all the lines in a paragraph and after
       determining the cutting state of the paragraph, but before trying to further parse or
       interpret them. After preprocess_paragraph() returns, the current cutting state (which is
       returned by "$self->cutting()") is examined. If it evaluates to true then input text
       (including the given $text) is cut (not processed) until the next POD directive is
       encountered.

       Please note that the preprocess_line() method is invoked before the preprocess_paragraph()
       method. After all (possibly preprocessed) lines in a paragraph have been assembled
       together and either it has been determined that the paragraph is part of the POD
       documentation from one of the selected sections or the "-want_nonPODs" option is true,
       then preprocess_paragraph() is invoked.

       The base class implementation of this method returns the given text.

METHODS FOR PARSING AND PROCESSING
       Pod::Parser provides several methods to process input text. These methods typically won't
       need to be overridden (and in some cases they can't be overridden), but subclasses may
       want to invoke them to exploit their functionality.

parse_text()
		   $ptree1 = $parser->parse_text($text, $line_num);
		   $ptree2 = $parser->parse_text({%opts}, $text, $line_num);
		   $ptree3 = $parser->parse_text(\%opts, $text, $line_num);

       This method is useful if you need to perform your own interpolation of interior sequences
       and can't rely upon interpolate to expand them in simple bottom-up order.

       The parameter $text is a string or block of text to be parsed for interior sequences; and
       the parameter $line_num is the line number corresponding to the beginning of $text.

       parse_text() will parse the given text into a parse-tree of "nodes."  and interior-
       sequences.  Each "node" in the parse tree is either a text-string, or a
       Pod::InteriorSequence.  The result returned is a parse-tree of type Pod::ParseTree. Please
       see Pod::InputObjects for more information about Pod::InteriorSequence and Pod::ParseTree.

       If desired, an optional hash-ref may be specified as the first argument to customize
       certain aspects of the parse-tree that is created and returned. The set of recognized
       option keywords are:

       -expand_seq => code-ref|method-name
	  Normally, the parse-tree returned by parse_text() will contain an unexpanded
	  "Pod::InteriorSequence" object for each interior-sequence encountered. Specifying
	  -expand_seq tells parse_text() to "expand" every interior-sequence it sees by invoking
	  the referenced function (or named method of the parser object) and using the return
	  value as the expanded result.

	  If a subroutine reference was given, it is invoked as:

	    &$code_ref( $parser, $sequence )

	  and if a method-name was given, it is invoked as:

	    $parser->method_name( $sequence )

	  where $parser is a reference to the parser object, and $sequence is a reference to the
	  interior-sequence object.  [NOTE: If the interior_sequence() method is specified, then
	  it is invoked according to the interface specified in "interior_sequence()"].

       -expand_text => code-ref|method-name
	  Normally, the parse-tree returned by parse_text() will contain a text-string for each
	  contiguous sequence of characters outside of an interior-sequence. Specifying
	  -expand_text tells parse_text() to "preprocess" every such text-string it sees by
	  invoking the referenced function (or named method of the parser object) and using the
	  return value as the preprocessed (or "expanded") result. [Note that if the result is an
	  interior-sequence, then it will not be expanded as specified by the -expand_seq option;
	  Any such recursive expansion needs to be handled by the specified callback routine.]

	  If a subroutine reference was given, it is invoked as:

	    &$code_ref( $parser, $text, $ptree_node )

	  and if a method-name was given, it is invoked as:

	    $parser->method_name( $text, $ptree_node )

	  where $parser is a reference to the parser object, $text is the text-string
	  encountered, and $ptree_node is a reference to the current node in the parse-tree
	  (usually an interior-sequence object or else the top-level node of the parse-tree).

       -expand_ptree => code-ref|method-name
	  Rather than returning a "Pod::ParseTree", pass the parse-tree as an argument to the
	  referenced subroutine (or named method of the parser object) and return the result
	  instead of the parse-tree object.

	  If a subroutine reference was given, it is invoked as:

	    &$code_ref( $parser, $ptree )

	  and if a method-name was given, it is invoked as:

	    $parser->method_name( $ptree )

	  where $parser is a reference to the parser object, and $ptree is a reference to the
	  parse-tree object.

interpolate()
		   $textblock = $parser->interpolate($text, $line_num);

       This method translates all text (including any embedded interior sequences) in the given
       text string $text and returns the interpolated result. The parameter $line_num is the line
       number corresponding to the beginning of $text.

       interpolate() merely invokes a private method to recursively expand nested interior
       sequences in bottom-up order (innermost sequences are expanded first). If there is a need
       to expand nested sequences in some alternate order, use parse_text instead.

parse_from_filehandle()
		   $parser->parse_from_filehandle($in_fh,$out_fh);

       This method takes an input filehandle (which is assumed to already be opened for reading)
       and reads the entire input stream looking for blocks (paragraphs) of POD documentation to
       be processed. If no first argument is given the default input filehandle "STDIN" is used.

       The $in_fh parameter may be any object that provides a getline() method to retrieve a
       single line of input text (hence, an appropriate wrapper object could be used to parse
       PODs from a single string or an array of strings).

       Using "$in_fh->getline()", input is read line-by-line and assembled into paragraphs or
       "blocks" (which are separated by lines containing nothing but whitespace). For each block
       of POD documentation encountered it will invoke a method to parse the given paragraph.

       If a second argument is given then it should correspond to a filehandle where output
       should be sent (otherwise the default output filehandle is "STDOUT" if no output
       filehandle is currently in use).

       NOTE: For performance reasons, this method caches the input stream at the top of the stack
       in a local variable. Any attempts by clients to change the stack contents during
       processing when in the midst executing of this method will not affect the input stream
       used by the current invocation of this method.

       This method does not usually need to be overridden by subclasses.

parse_from_file()
		   $parser->parse_from_file($filename,$outfile);

       This method takes a filename and does the following:

       o opens the input and output files for reading (creating the appropriate filehandles)

       o invokes the parse_from_filehandle() method passing it the corresponding input and output
	 filehandles.

       o closes the input and output files.

       If the special input filename "-" or "<&STDIN" is given then the STDIN filehandle is used
       for input (and no open or close is performed). If no input filename is specified then "-"
       is implied. Filehandle references, or objects that support the regular IO operations (like
       "<$fh>" or "$fh-<Egt"getline>) are also accepted; the handles must already be opened.

       If a second argument is given then it should be the name of the desired output file. If
       the special output filename "-" or ">&STDOUT" is given then the STDOUT filehandle is used
       for output (and no open or close is performed). If the special output filename ">&STDERR"
       is given then the STDERR filehandle is used for output (and no open or close is
       performed). If no output filehandle is currently in use and no output filename is
       specified, then "-" is implied.	Alternatively, filehandle references or objects that
       support the regular IO operations (like "print", e.g. IO::String) are also accepted; the
       object must already be opened.

       This method does not usually need to be overridden by subclasses.

ACCESSOR METHODS
       Clients of Pod::Parser should use the following methods to access instance data fields:

errorsub()
		   $parser->errorsub("method_name");
		   $parser->errorsub(\&warn_user);
		   $parser->errorsub(sub { print STDERR, @_ });

       Specifies the method or subroutine to use when printing error messages about POD syntax.
       The supplied method/subroutine must return TRUE upon successful printing of the message.
       If "undef" is given, then the carp builtin is used to issue error messages (this is the
       default behavior).

		   my $errorsub = $parser->errorsub()
		   my $errmsg = "This is an error message!\n"
		   (ref $errorsub) and &{$errorsub}($errmsg)
		       or (defined $errorsub) and $parser->$errorsub($errmsg)
			   or  carp($errmsg);

       Returns a method name, or else a reference to the user-supplied subroutine used to print
       error messages. Returns "undef" if the carp builtin is used to issue error messages (this
       is the default behavior).

cutting()
		   $boolean = $parser->cutting();

       Returns the current "cutting" state: a boolean-valued scalar which evaluates to true if
       text from the input file is currently being "cut" (meaning it is not considered part of
       the POD document).

		   $parser->cutting($boolean);

       Sets the current "cutting" state to the given value and returns the result.

parseopts()
       When invoked with no additional arguments, parseopts returns a hashtable of all the
       current parsing options.

		   ## See if we are parsing non-POD sections as well as POD ones
		   my %opts = $parser->parseopts();
		   $opts{'-want_nonPODs}' and print "-want_nonPODs\n";

       When invoked using a single string, parseopts treats the string as the name of a parse-
       option and returns its corresponding value if it exists (returns "undef" if it doesn't).

		   ## Did we ask to see '=cut' paragraphs?
		   my $want_cut = $parser->parseopts('-process_cut_cmd');
		   $want_cut and print "-process_cut_cmd\n";

       When invoked with multiple arguments, parseopts treats them as key/value pairs and the
       specified parse-option names are set to the given values. Any unspecified parse-options
       are unaffected.

		   ## Set them back to the default
		   $parser->parseopts(-warnings => 0);

       When passed a single hash-ref, parseopts uses that hash to completely reset the existing
       parse-options, all previous parse-option values are lost.

		   ## Reset all options to default
		   $parser->parseopts( { } );

       See "PARSING OPTIONS" for more information on the name and meaning of each parse-option
       currently recognized.

output_file()
		   $fname = $parser->output_file();

       Returns the name of the output file being written.

output_handle()
		   $fhandle = $parser->output_handle();

       Returns the output filehandle object.

input_file()
		   $fname = $parser->input_file();

       Returns the name of the input file being read.

input_handle()
		   $fhandle = $parser->input_handle();

       Returns the current input filehandle object.

PRIVATE METHODS AND DATA
       Pod::Parser makes use of several internal methods and data fields which clients should not
       need to see or use. For the sake of avoiding name collisions for client data and methods,
       these methods and fields are briefly discussed here. Determined hackers may obtain further
       information about them by reading the Pod::Parser source code.

       Private data fields are stored in the hash-object whose reference is returned by the new()
       constructor for this class. The names of all private methods and data-fields used by
       Pod::Parser begin with a prefix of "_" and match the regular expression "/^_\w+$/".

TREE-BASED PARSING
       If straightforward stream-based parsing wont meet your needs (as is likely the case for
       tasks such as translating PODs into structured markup languages like HTML and XML) then
       you may need to take the tree-based approach. Rather than doing everything in one pass and
       calling the interpolate() method to expand sequences into text, it may be desirable to
       instead create a parse-tree using the parse_text() method to return a tree-like structure
       which may contain an ordered list of children (each of which may be a text-string, or a
       similar tree-like structure).

       Pay special attention to "METHODS FOR PARSING AND PROCESSING" and to the objects described
       in Pod::InputObjects. The former describes the gory details and parameters for how to
       customize and extend the parsing behavior of Pod::Parser. Pod::InputObjects provides
       several objects that may all be used interchangeably as parse-trees. The most obvious one
       is the Pod::ParseTree object. It defines the basic interface and functionality that all
       things trying to be a POD parse-tree should do. A Pod::ParseTree is defined such that each
       "node" may be a text-string, or a reference to another parse-tree.  Each Pod::Paragraph
       object and each Pod::InteriorSequence object also supports the basic parse-tree interface.

       The parse_text() method takes a given paragraph of text, and returns a parse-tree that
       contains one or more children, each of which may be a text-string, or an InteriorSequence
       object. There are also callback-options that may be passed to parse_text() to customize
       the way it expands or transforms interior-sequences, as well as the returned result. These
       callbacks can be used to create a parse-tree with custom-made objects (which may or may
       not support the parse-tree interface, depending on how you choose to do it).

       If you wish to turn an entire POD document into a parse-tree, that process is fairly
       straightforward. The parse_text() method is the key to doing this successfully. Every
       paragraph-callback (i.e. the polymorphic methods for command(), verbatim(), and
       textblock() paragraphs) takes a Pod::Paragraph object as an argument. Each paragraph
       object has a parse_tree() method that can be used to get or set a corresponding parse-
       tree. So for each of those paragraph-callback methods, simply call parse_text() with the
       options you desire, and then use the returned parse-tree to assign to the given paragraph
       object.

       That gives you a parse-tree for each paragraph - so now all you need is an ordered list of
       paragraphs. You can maintain that yourself as a data element in the object/hash. The most
       straightforward way would be simply to use an array-ref, with the desired set of custom
       "options" for each invocation of parse_text. Let's assume the desired option-set is given
       by the hash %options. Then we might do something like the following:

	   package MyPodParserTree;

	   @ISA = qw( Pod::Parser );

	   ...

	   sub begin_pod {
	       my $self = shift;
	       $self->{'-paragraphs'} = [];  ## initialize paragraph list
	   }

	   sub command {
	       my ($parser, $command, $paragraph, $line_num, $pod_para) = @_;
	       my $ptree = $parser->parse_text({%options}, $paragraph, ...);
	       $pod_para->parse_tree( $ptree );
	       push @{ $self->{'-paragraphs'} }, $pod_para;
	   }

	   sub verbatim {
	       my ($parser, $paragraph, $line_num, $pod_para) = @_;
	       push @{ $self->{'-paragraphs'} }, $pod_para;
	   }

	   sub textblock {
	       my ($parser, $paragraph, $line_num, $pod_para) = @_;
	       my $ptree = $parser->parse_text({%options}, $paragraph, ...);
	       $pod_para->parse_tree( $ptree );
	       push @{ $self->{'-paragraphs'} }, $pod_para;
	   }

	   ...

	   package main;
	   ...
	   my $parser = new MyPodParserTree(...);
	   $parser->parse_from_file(...);
	   my $paragraphs_ref = $parser->{'-paragraphs'};

       Of course, in this module-author's humble opinion, I'd be more inclined to use the
       existing Pod::ParseTree object than a simple array. That way everything in it, paragraphs
       and sequences, all respond to the same core interface for all parse-tree nodes. The result
       would look something like:

	   package MyPodParserTree2;

	   ...

	   sub begin_pod {
	       my $self = shift;
	       $self->{'-ptree'} = new Pod::ParseTree;	## initialize parse-tree
	   }

	   sub parse_tree {
	       ## convenience method to get/set the parse-tree for the entire POD
	       (@_ > 1)  and  $_[0]->{'-ptree'} = $_[1];
	       return $_[0]->{'-ptree'};
	   }

	   sub command {
	       my ($parser, $command, $paragraph, $line_num, $pod_para) = @_;
	       my $ptree = $parser->parse_text({<<options>>}, $paragraph, ...);
	       $pod_para->parse_tree( $ptree );
	       $parser->parse_tree()->append( $pod_para );
	   }

	   sub verbatim {
	       my ($parser, $paragraph, $line_num, $pod_para) = @_;
	       $parser->parse_tree()->append( $pod_para );
	   }

	   sub textblock {
	       my ($parser, $paragraph, $line_num, $pod_para) = @_;
	       my $ptree = $parser->parse_text({<<options>>}, $paragraph, ...);
	       $pod_para->parse_tree( $ptree );
	       $parser->parse_tree()->append( $pod_para );
	   }

	   ...

	   package main;
	   ...
	   my $parser = new MyPodParserTree2(...);
	   $parser->parse_from_file(...);
	   my $ptree = $parser->parse_tree;
	   ...

       Now you have the entire POD document as one great big parse-tree. You can even use the
       -expand_seq option to parse_text to insert whole different kinds of objects. Just don't
       expect Pod::Parser to know what to do with them after that. That will need to be in your
       code. Or, alternatively, you can insert any object you like so long as it conforms to the
       Pod::ParseTree interface.

       One could use this to create subclasses of Pod::Paragraphs and Pod::InteriorSequences for
       specific commands (or to create your own custom node-types in the parse-tree) and add some
       kind of emit() method to each custom node/subclass object in the tree. Then all you'd need
       to do is recursively walk the tree in the desired order, processing the children (most
       likely from left to right) by formatting them if they are text-strings, or by calling
       their emit() method if they are objects/references.

CAVEATS
       Please note that POD has the notion of "paragraphs": this is something starting after a
       blank (read: empty) line, with the single exception of the file start, which is also
       starting a paragraph. That means that especially a command (e.g. "=head1") must be
       preceded with a blank line; "__END__" is not a blank line.

SEE ALSO
       Pod::InputObjects, Pod::Select

       Pod::InputObjects defines POD input objects corresponding to command paragraphs, parse-
       trees, and interior-sequences.

       Pod::Select is a subclass of Pod::Parser which provides the ability to selectively include
       and/or exclude sections of a POD document from being translated based upon the current
       heading, subheading, subsubheading, etc.

AUTHOR
       Please report bugs using <http://rt.cpan.org>.

       Brad Appleton <bradapp@enteract.com>

       Based on code for Pod::Text written by Tom Christiansen <tchrist@mox.perl.com>

LICENSE
       Pod-Parser is free software; you can redistribute it and/or modify it under the terms of
       the Artistic License distributed with Perl version 5.000 or (at your option) any later
       version. Please refer to the Artistic License that came with your Perl distribution for
       more details. If your version of Perl was not distributed under the terms of the Artistic
       License, than you may distribute PodParser under the same terms as Perl itself.

perl v5.16.3				    2013-06-01				   Pod::Parser(3)
Unix & Linux Commands & Man Pages : ©2000 - 2018 Unix and Linux Forums


All times are GMT -4. The time now is 04:30 PM.